CNC Precision Machining: What Engineers Should Consider In Their Design Process

Precision Machining By Ben Machine

You’ve been assigned a component to draw up to be machined.  Drawing it up isn’t an issue, but how much consideration do you give to making your design efficient?  Regardless of what the part is actually designed to do, there are invariably aspects of its manufacture that you as an engineer can optimize.

Material Considerations

Take the material for example.  A specific metal alloy isn’t better or worse than another alloy.  They have different properties. One stands up better to acids, while another is better against salt water.  One is harder while another machines better.  You want to choose the material according to the needs of the component, of course, but it makes sense to consider the cost as well.  Some alloys can be twice the price of others simply because of their chemistry.  Will the lower-priced stock work just as well for your needs?  That saves the company and your customer money.

Do you put any thought into the form of raw stock?  Most bulk metals come in standard sizes.  If you have the latitude in your design, you can help realize big savings by designing with an eye to the raw stock.  For instance, if you design a component to be .75” thick, that’s a standard bar stock size.  Which means you really need to cut it from the next size up (1” stock) and mill it down to the finished thickness.  If you can design that component to be .65” thick, you can use .75” stock, saving the customer more money.  Likewise, how does your design relate to the length and width of your raw stock?  If your stock comes in eight-foot lengths, for example, and your component is 16” long, you’ll get five out of each piece because even with CNC Precision Machining there are kerfs from cutting them apart.  If you can design the component to be 15”, you’ll get an extra one from each piece of raw material, and a lot less waste.


One consideration that comes up is the options of how to arrange connections and other features.  Depending on the latitude given, and the functionality of the component, minimizing lateral holes and other features -basically simplifying the design- can greatly speed up the CNC Machining.

When designing the various features of a component, a responsible engineer will always keep in mind the realities of manufacturing it.  Saddle curves are beautiful, and they have their place, but they’re not exactly easy to secure to a mill table.  Avoid compound curves in favour of shapes that are easy to clamp down to a mill table.  Even having to use screw-down clamps slows production.  Speed things up by providing through screw holes if a vise isn’t sufficient.  The slowest part of CNC Machining is often opening the machine to reposition the component.  Taking steps to make the component easy to lock down, including avoiding having to turn it unnecessarily during milling will save the customer money.


Customers will often specify the milling surface requirements and surface finishing required for given points on a component.  That doesn’t necessarily mean that all surfaces have to meet those requirements.  The CNC machine process may have to focus on control or contact surfaces, but other surfaces are often less critical.  Your design can specify the extra attention to be paid where needed while avoiding wasting money polishing or treating areas that simply don’t matter.

Design to Succeed

You never want to compromise functionality, but over-engineering can cause a component to fail in a different way.  Produce it from oversized bars of the most expensive material.  Specify tolerances that triple the number of finish steps.  Sculpt it to look like modern art so milling it requires special holding fixtures.  Order the most durable finishes designed to withstand environments it will never see.  You will design a component that costs your customer triple what it could realistically cost -what their competitor will pay for their version.  Perfection is a lofty goal, but is perfect in every possible aspect really better than perfection in the ways that actually matter to the people that use your work?

The professionals at Ben Machine understand this.  We value “perfection” in the CNC machining process.  Our clients know what they need their parts to do, but they often don’t know the practical considerations of the machining process itself.  That’s why we love to work with engineers as they design their parts.  Two areas of expertise coming together to produce something new will always benefit from having professionals from both sides fine-tuning the design together.  It maximizes the speed of production, and quality of the finished product while minimizing the cost.  This is where Ben Machine truly excels.